By default, Firefox automatically backs up your current bookmarks to a .json file under the current user profile, usually a path like ".mozilla/firefox/xxxx.default/bookmarkbackups". Some of us still like to work with the old-school HTML export instead.
To enable automatic backups of bookmarks to HTML, you need to add the following through either "about:config" or in the optional user.js config file (where customizations to prefs.js can be added). The backup will be created and then overwritten every time the browser is closed.
If doing this through about:config, search for browser.bookmarks.autoExportHTML (if it doesn't exist, create it as a boolean item), and set to true. Then create the browser.bookmarks.file item as a string item and enter the full path for the file (e.g., /home/myuser/bookmarks.html, where "myuser" is your login name on the system).
Before making the change in user.js (located at ~/.mozilla/firefox/xxx.default, if it doesn't exist c